A stretching and blow-molding apparatus for producing hollow bodies from thermoplastic plastics materials is known. Such an apparatus comprises a rotatable wheel assembly on which a plurality of blow molds are mounted. The two halves of each mold are mounted on a common pivot axis to allow the mold to be opened and closed. The apparatus further includes locking claws or pawls which are disposed on the curved external surface of each mold half. These claws or pawls extend beyond the mold centre-line when the mold is closed and interdigitate with one another. Longitudinally displaceable locking members are provided for locking the pawls or claws together. A locking device for use is a stretching and blow-molding apparatus is disclosed in German Patent Specification No. 3336071. However, such device only permits the mold halves to be locked together at two points. Moreover, such a locking device necessitates the use of long lever rods which need to be actuated by a cam system and by a sliding cam controller.